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Electronics Letters

Highly efficient photon-pair source usingperiodically poled lithium niobate waveguide

Sébastien Tanzilli, Hugues de Riedmatten, Wolfgang Tittel, Hugo Zbinden, Pascal A. Baldi, Marc de Micheli, Daniel B. Ostrowsky, Nicolas Gisin

Published Jan 4, 2001• 380 citations
Publisher

Abstract

A new kind of correlated photon-pair source based on a waveguide integrated on a periodically poled lithium niobate substrate is reported. Using a pump laser of a few µW at 657 nm, photon-pairs are generated/degenerated at 1314 nm. Detecting ~1500 coincidences per second, a conversion rate of 10-6 pairs per pump photon can be inferred, which is four orders of magnitude higher than that obtained with previous bulk sources. These results are very promising for the realisation of sources for quantum communication and quantum metrology experiments requiring a high signal-to-noise ratio or working with more than one photon-pair at a time.

DOI
10.1049/el:20010009

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arXiv:2510.03619•Oct 4, 2025•0 citations
A new kind of correlated photon-pair source based on a waveguide integrated on a periodically poled lithium niobate substrate is reported. Using a pump laser of a few µW at 657 nm, photon-pairs are generated/degenerated at 1314 nm. Detecting ~1500 coincidences per second, a conversion rate of 10-6 pairs per pump photon can be inferred, which is four orders of magnitude higher than that obtained with previous bulk sources. These results are very promising for the realisation of sources for quantum communication and quantum metrology experiments requiring a high signal-to-noise ratio or working with more than one photon-pair at a time.
We report on a new kind of correlated photon-pair source based on a waveguide integrated on a Periodically Poled Lithium Niobate substrate. Using a pump laser of a few micro-Watts at 657 nm, we generate degenerate photon-pairs at 1314 nm. Detecting about 1500 coincidences per second, we can infer a conversion rate of 10-6 pairs per pump photon, which is four orders of magnitude higher than that obtained with previous bulk sources. These results are very promising for the realization of sources for quantum communication and quantum metrology experiments requiring a high signal-to-noise ratio or working with more than one photon-pair at a time.
Reliable generation of single photons is of key importance for fundamental physical experiments and quantum protocols.The periodically poled lithium niobate (LN) waveguide has shown promise for an integrated quantum source due to its large spectral tunability and high efficiency, benefiting from the quasi-phase-matching.Here we demonstrate photon-pair sources based on an LN waveguide periodically poled by a tightly focused femtosecond laser beam.The pair coincidence rate reaches ∼8000 counts per second for average pump power of 3.2 mW (peak power is 2.9 kW).Our results prove the possibility of application of the nonlinear photonics structure fabricated by femtosecond laser to the integrated quantum source.This method can be extended to three-dimensional domain structures, which provide a potential platform for steering the spatial degree of freedom of the entangled two-photon states.
Efficient on-chip entangled photon pair generation at telecom wavelengths is an integral aspect of emerging quantum optical technologies, particularly for quantum communication and computing. However, moving to shorter wavelengths enables the use of more accessible silicon detector technology, and opens up applications in imaging and spectroscopy. Here, we present high brightness ((1.6 ± 0.3) × 10 9 pairs/s/mW/nm) visible–near-IR photon pair generation in a periodically poled lithium niobate nanophotonic waveguide. The degenerate spectrum of the photon pairs is centered at 811 nm with a bandwidth of 117 nm when pumped with a spectrally multimode laser diode. The measured on-chip source efficiency of (2.3 ± 0.5) × 10 11 pairs/s/mW is on par with source efficiencies at telecom wavelengths and is also orders of magnitude higher than the efficiencies of other visible sources implemented in bulk crystal or diffused waveguide-based technologies. Further improvements in the brightness and efficiencies are possible by pumping the device with a single-frequency laser, which would also shrink the pair bandwidth. These results represent the shortest wavelength of photon pairs generated in a nanophotonic waveguide reported to date by nearly an octave.
In this paper we measure the efficiency of photon pair production from parametric downconversion at the photon counting level, generated in a laboratory prototype of PPLN waveguide at 1572 nm. The aim is to enhance the brightness of an heralded single photon source and to improve compactness for quantum communication applications, namely quantum key distribution. We observed a maximum of the conversion efficiency corresponding to 7.9 106 photon pairs/s for a pump power of 28 μW. This value is compared with the measured pairs production in a classical experiment of difference frequency generation, realized with the same sample by analogue classical detection. We highlight the advantages of using the waveguide versus a bulk PPLN for such applications and we foresee further possible improvements by adopting waveguide in a single photon level experimental setup.
Summary form only given. Recent progress in quantum information processing has highlighted the benefits of integrated optic devices for quantum applications (e.g.[l]). The miniaturization of systems with increased complexity drastically reduces the required space and paves the way for future commercialization.In the past five years, several groups have demonstrated promising approaches to achieve quantum interference and photonic gates on-chip (e.g.[2]). However, in all of these experiments the preparation of the photon pairs has been performed outside the integrated devices employing bulk crystal parametric down-conversion (PDC) sources, while the efficient coupling between these sources and the integrated circuit remains as a bottleneck for the design of systems with increasing complexity. On the other hand remarkable efforts have been devoted to the development of integrated PDC sources for photon pair generation inside channel waveguides [3]. The main benefits of guided-wave PDC processes include high conversion efficiencies and spatial mode control. We combine the prospects of an efficient type-I PDC source based on Titanium-indiffused periodically poled Z-cut Lithium Niobate waveguides (Ti:PPLN) with a passive wavelength division demultiplexing coupler on-chip, shown in Figure 1. The coupler allows for excellent spatial separation generated photon pairs. The non-degenerate decay of pump photons at 532 nm into signal and idler photons provides us with a photon pair at wavelengths of 1575 nm and 800 nm, respectively. Thus low-loss fiber transmission of the prepared states at 1575 nm can be accomplished on the one hand, while on the other hand efficient heralding of conditioned states can be implemented with off-the-shelf silicon-based detectors. The quality and efficiency of our source was improved by the deposition of endface-coatings. This allows for the efficient launching of pump light into the waveguide and it simultaneously provides a close-toperfect transmission of signal and idler at the output of our source, reflecting the pump light by more than 99%. In conditioned coincidence measurements in the picosecond pulsed regime we achieved heralding of single photons with almost no influence of background radiation, expressed by high coincidences-toaccidentals ratios up to CAR > 7400. The preparation exceeded 60% of efficiency in the low pump power regime, accompanied with ultra-low second-order correlation functions of g(2) (0) <; 4.10-3. These figures of merit in conjunction with the integration of active and passive elements make our source a candidate for a basic building block in more complex and miniaturized quantum network realizations in the future.
Broadband nonlinear optical devices play a critical role in both classical and quantum optics. Here, we design and fabricate a 6.82-mm-long step-chirped periodically poled lithium niobate~(CPPLN) waveguide on lithium niobate on insulator, which enables quasi-phase matching over a broad bandwidth for second-harmonic generation~(SHG) and spontaneous parametric down-conversion~(SPDC). The SHG achieves an average efficiency of 54.4\%/W/cm2^22 over the first-harmonic wavelength range of 1510~nm-1620~nm, paving the way for realizing SPDC across a wide range of pump wavelengths. For SPDC, by tuning the pump wavelength to 775~nm, 780~nm, and 785~nm, we achieve broadband photon-pair generation with a maximum full bandwidth and brightness up to 99~THz~(846~nm) and 20~GHz/mW/nm, respectively. Our findings provide an efficient and experiment-friendly approach for generating broadband photon pairs, which holds significant promise for advancing applications in quantum metrology.